A seat provided in a vehicle is configured to include a seat back supporting a lower body of a passenger, a seat cushion supporting a lower body of the passenger such as hips, thighs, and the like, and a head rest supporting the back of a head of the passenger, wherein a reclining apparatus enabling adjustment of an angle of the seat back with respect to the seat cushion is mounted at a portion at which the seat back and the seat cushion are connected to each other.
As the reclining apparatus, there are a manual type reclining apparatus adjusting an angle of the seat back by a lever manipulation by the passenger and a power type reclining apparatus automatically operated by power of a motor through a switch manipulation.
The reclining apparatuses generally include components coupled with the seat back and components coupled with the seat cushion independent of an operation scheme, and the components coupled with the seat back may be relatively rotated to the components coupled with the seat cushion to adjust the angle of the seat back.
FIG. 1 is a diagram illustrating a gear plate 1 which is a component coupled with the seat cushion, in which a center of the gear plate is provided with a center hole 1a and an external gear 2 is protrudedly formed around the center hole 1a. 
Further, a flange part 3 is formed around the external gear 2 and a plurality of coupling protrusions 4 are coupled with the flange part 3 by welding so that the gear plate 1 may be coupled with the seat cushion (not illustrated). In this case, the external gear 2 may be protrudedly formed on one surface of the gear plate 1 and the coupling protrusion 4 may be protrudedly formed on the other surface of the gear plate 1.
Further, although not illustrated in the drawings, as a component coupled with the seat back, a mobile flange is provided. An inside of the mobile flange is provided with an internal gear and an operating unit for eccentrically rotating the mobile flange is provided between the gear plate and the mobile flange. That is, the mobile flange is rotated while the external gear on the gear plate being engaged with the internal gear, such that the seat back coupled with the mobile flange is rotated to adjust the angle of the seat back.
However, in the case of the above-mentioned gear plate, since the coupling protrusion is positioned at an edge portion of the external gear, the flange part needs to be provided around the external gear to form the coupling protrusion. In this case, since the flange part is provided along the edge of the external gear, it is very difficult to reduce a weight of the gear plate due to the flange part.
Further, since the coupling protrusion is coupled with the flange part by the welding, man hour may be increased and production and manufacturing costs of components may be increased.
Further, since the operating unit provided between the gear plate and the mobile flange is configured to be exposed to the outside, components configuring the operating unit may be separated.
The contents described as the related art have been provided only for assisting in the understanding for the background of the present invention and should not be considered as corresponding to the related art known to those skilled in the art.